Resistance-reducing conductive adhesives for attachment of electronic components

ABSTRACT

Resistance-reducing conductive adhesives, and apparatus and methods of attaching electronic components using resistance-reducing conductive adhesives are provided. In one embodiment, a resistance-reducing conductive adhesive includes a first quantity of conductive adhesive, and a second quantity of a chelating agent combined with the conductive adhesive. The chelating agent reacts with an oxidized conductive material (e.g. alumina or aluminum ion) on a conductive lead to form soluble conductive metal-ligand complex. The chelating agent may also passivate the oxide-free conductive material by forming hydrogen bonds. The resistance of the resulting electrical connection is reduced in comparison with prior art methods of conductive adhesive coupling, providing improved signal strength, reduced power consumption, and decreased waste heat. In alternate embodiments, the conductive adhesive may include an anisotropically conductive adhesive, an isotropically conductive adhesive, a conductive epoxy, or a hydrophilic adhesive.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.09/561,030, filed Apr. 28, 2000 now U.S. Pat. No. 6,346,750.

TECHNICAL FIELD

The present invention relates to resistance-reducing conductiveadhesives, and to apparatus and methods of attaching electroniccomponents using resistance-reducing conductive adhesives.

BACKGROUND OF THE INVENTION

Semiconductor chips (or die) may be mounted to circuit boards or otherelectronic components in several ways. FIG. 1 shows a die 10 mounted toa circuit board 20 in a “flip chip” or “chip on board” (COB) assembly.In this assembly, the die 10 has a pair of bond pads 12 that areattached directly to a corresponding pair of contact pads 22 on thecircuit board 20. The bond pads 12 and contact pads 22 are typicallyformed from aluminum, although other electrically conductive materialsmay be used. The bond pads 12 may be attached to the contact pads 22 bysoldering or by some other suitable method. Electrical signals from thecircuit board 20 may then be transmitted to the internal circuitry (notshown) of the die 10 through the contact pads 22 to the bond pads 12,and vice versa. It is customary to provide an encapsulating layer (or“glob top”) 14 over the die 10 to hermetically seal the die 10, thusinsulating and protecting the die 10 from humidity, oxidation, and otherharmful elements.

It is known to use a layer of conductive material to attach the bondpads of a die to the contact pads of a circuit board, as disclosed inU.S. Pat. No. 5,789,278, and in commonly-owned co-pending patentapplication Ser. No. 09/389,862, both incorporated herein by reference.For example, FIG. 2 is a partial cross-sectional view of a bumped die 40attached to a circuit board 20 using an anisotropically conductive layer50. In this assembly, solder bumps 42 are formed on the bond pads 12 ofthe die 40. The anisotropically conductive layer 50 is formed betweenthe bond pads 12 and the contact pads 22 on the circuit board 20.

The anisotropically conductive layer 50 includes a plurality ofconductive particles 52 distributed in a suspension material 54,providing electrically conductive pathways 56 through the suspensionmaterial 54 in one direction (e.g. the “z” direction as shown in FIG.3). The conductive pathways 56 may be formed, for example, bycompressing the solder bumps 42 against the layer 50, causing theconductive particles 52 to contact each other to form columns ofconductive particles. Electrical signals are then transmitted from thecircuit board 20 to the die 40 through the conductive pathways 56, andvice versa. The layer 50 is electrically insulative all otherdirections, hence it is “anisotropically” conductive.

Anisotropically conductive layers 50 may be formed in a number of ways,including as a film or as a viscous paste that is applied (e.g.stenciled, sprayed, flowed, etc.) to the circuit board 20 and thecontact pads 22. The anisotropically conductive layers 50 may then becured by, for example, subjecting the suspension material 54 to certainenvironmental conditions (e.g. temperature, pressure, etc.), exposing tosuitable curing compounds, irradiating with ultraviolet or ultrasonicenergy, or other means depending on the composition of the suspensionmaterial 54. The suspension material 54 may be composed of a variety ofmaterials, including thermoset polymers, B-stage (or “pre-preg”)polymers, pre-B stage polymers, thermoplastic polymers, or any monomer,polymer, or other suitable material that is non-conductive and cansupport the conductive particles 52. Various suspension materials aretaught, for example, in U.S. Pat. No. 5,221,417 to Basavanhally and inU.S. Pat. No. 4,737,112 to Jin et al. The conductive particles 52 arecommonly formed from silver, nickel, or gold, however, a variety ofelectrically conductive particles may be used.

Isotropically conductive layers may also be used for attachment ofelectronic components. For example, FIG. 3 is a partial cross-sectionalview of a die 10 having a pair of bond pads 12, each bond pad 12 beingattached to corresponding contact pads 22 of a circuit board 20 by anisotropically conductive layer 60. Like the anisotropically conductivelayer 50 described above, each isotropically conductive layer 60includes a plurality of conductive particles 62 suspended in asuspension material 64. The isotropically conductive layer 60, however,is electrically conductive in all directions and therefore does notextend between adjacent bond pads 12 (or contact pads 22) to preventshorting or erroneous signals. Electrical signals from the circuit board20 are transmitted through the isotropically conductive layers 60 to thedie 10, and vice versa. Both isotropic and anisotropic conductivematerials are commercially-available from, for example, Ablestik ofRancho Dominguez, Calif., or A.I. Technology, Inc. of Trenton, N.J., orSheldahl, Inc. of Northfield, Minn., or 3M of St. Paul, Minn.

Although successful results have been achieved using theabove-referenced die packages, there is room for improvement. Forexample, each of the electrical connections between the bond pads 12 andthe contact pads 22 are electrically resistive which may reduce signalstrength, increase power consumption, and increase waste heatgeneration. These characteristics may undesirably degrade theperformance of an electronic assembly.

SUMMARY OF THE INVENTION

The present invention is directed to resistance-reducing conductiveadhesives, and to apparatus and methods of attaching electroniccomponents using resistance-reducing conductive adhesives. In oneaspect, a resistance-reducing conductive adhesive comprises a firstquantity of conductive adhesive, and a second quantity of a chelatingagent combined with the conductive adhesive. The chelating agent reactswith a metal, typically an oxidized form of the metal such as an oxideor metal ion of a metal-containing conductive lead (or other electroniccomponent) to form a soluble metal-ligand complex. The chelating agentmay also react with an oxide-free form of the metal on the conductivelead to passivate the metal by forming hydrogen bonds. The resistance ofthe resulting electrical connection is reduced in comparison with priorart methods of conductive adhesive coupling, providing improved signalstrength, reduced power consumption, and decreased waste heat.

In various alternate aspects, the conductive adhesive may comprise ananisotropically conductive adhesive, an isotropically conductiveadhesive, a conductive epoxy, or a hydrophilic adhesive. In otheraspects, the chelating agent reacts with a lead comprising anotherconductive material, particularly a metal. Typically, the metal is adivalent or trivalent metal, including but not limited to, aluminum,copper, gold, nickel, platinum or silver. In a preferred aspect, themetal is aluminum. Alternately, the chelating agents may be any suitableagent that provides the desired reactive mechanisms, including, forexample, oxalic acid, malonic acid, citric acid, and succinate succinicacid. In a further aspect, the second quantity of the chelating agentcomprises a value within the range from approximately 0.1 percent byweight to approximately 20 percent by weight, inclusive.

In another aspect, an electronic assembly comprises a first componenthaving a first conductive lead formed thereon, a second conductive lead,and a resistance-reducing conductive layer extending between the firstconductive lead and the second conductive lead. The resistance-reducingconductive layer comprises a conductive adhesive having a plurality ofconductive particles disposed within a suspension material, and achelating agent approximately uniformly blended with a portion of theconductive adhesive, the chelating agent being chemically reactive withan at least partially oxidized metal ion or metal-oxide to form asoluble conductive metal-ligand complex. The portion of the conductiveadhesive may include substantially the whole volume of the conductiveadhesive or be a local volume locally disposed between the conductiveleads. Alternately, the first component may comprise a die, a circuitboard, or any other electronic component.

In yet another aspect, a method of electrically coupling a firstconductive lead of an electronic component to a second conductive leadcomprises combining a conductive adhesive with a chelating agent to forma resistance-reducing conductive adhesive, the chelating agent beingchemically reactive with a metal component of the first or secondconductive leads to form a soluble metal-ligand complex, forming a layerof the resistance-reducing conductive adhesive proximate the first andsecond conductive leads, and engaging the first and second conductiveleads with the layer of resistance-reducing conductive adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view of a die mounted to a circuitboard in accordance with the prior art.

FIG. 2 is a partial cross-sectional view of a die mounted to a circuitboard using an anisotropically conductive layer in accordance with theprior art.

FIG. 3 is a partial cross-sectional view of a die mounted to a circuitboard using isotropically conductive layers in accordance with the priorart.

FIG. 4 is a partial cross-sectional view of an electrical connectionhaving a first conductive lead coupled to a second conductive lead usinga resistance-reducing conductive layer in accordance with an embodimentof the invention.

FIG. 5A is a schematic representation of a first mechanism of aresistance-reducing reaction in accordance with an embodiment of theinvention.

FIG. 5B is a schematic representation of a second mechanism of aresistance-reducing reaction in accordance with an embodiment of theinvention.

FIG. 6 is a partial cross-sectional view of an electronic assemblyhaving a resistance-reducing anisotropically conductive layer inaccordance with an alternate embodiment of the invention.

FIG. 7 is a partial cross-sectional view of a stacked die assemblyhaving a plurality of resistance-reducing isotropically conductivelayers in accordance with another embodiment of the invention.

FIG. 8 is a partial cross-sectional view of an electrical connection inaccordance with another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present description is generally directed toward resistance-reducingconductive adhesives, and to apparatus and methods of attachingelectronic components using resistance-reducing conductive adhesives.Many specific details of certain embodiments of the invention are setforth in the following description and in FIGS. 4-8 to provide athorough understanding of such embodiments. One skilled in the art willunderstand, however, that the present invention may have additionalembodiments, or that the present invention may be practiced withoutseveral of the details described in the following description. Althougha variety of electronic components may be attached in accordance withthe invention, to simplify the description to allow the reader to focuson the inventive aspects, several of the following embodiments of theinvention are described in terms of a semiconductor die attached to aprinted circuit board.

FIG. 4 is a partial cross-sectional view of an electrical connection 100having a first conductive lead 112 coupled to a second conductive lead114 using a resistance-reducing conductive layer 150 in accordance withan embodiment of the invention. In one embodiment, at least one of thefirst lead 112 and the second lead 114 are formed of divalent ortrivalent metal. In preferred embodiments, at least one lead, orpreferably both leads, are formed of aluminum. The resistance-reducingconductive layer 150 includes a plurality of conductive particles 152distributed in a modified suspension medium 154. The modified suspensionmedium 154 includes a suspension material 54 and a chelating agent 156.The chelating agent 156 is approximately uniformly blended into thesuspension material 54, and chemically reacts with the conductive leadin the first and second leads 112, 114, reducing the electricalresistivity of the electrical connection 100 compared with the prior artelectrical connections described above.

In one embodiment, the resistance-reducing conductive layer 150 includesa commercially-available anisotropically conductive adhesive,specifically, a product known as Ablebond® 8360 distributed by AblestikElectronic Materials & Adhesives of Rancho Dominguez, Calif. Ablebond®8360 includes silver particles suspended in an epoxy-type suspensionmaterial 54. As a chelating agent 156, a quantity of oxalic acid may beadded to the Ablebond® 8360 to form the resistance-reducing conductivelayer 150. Oxalic acid is commercially-available from a variety ofsources, including, for example, Integra Chemical Company of Renton,Wash.

It should be noted that a variety of chelating agents other than oxalicacid may be used, including but not limited to polydentate ligands.Typical polydentate ligands include compounds having dihydroxy,hydroxy-ketone, hydroxy-acid, diketone, and diacidic structures.Preferred polydentate ligands include for example, oxalic acid, malonicacid, a citric acid, and succinate succinic acid. Oxalitc, malanolitccitriatic and succinatic derivatives of these ligands are also useful.As used herein, oxalitic, malanolitc, citriatic or succinaticderivatives include compounds containing an oxalate, malonate, citrateor succinate moiety, respectively, which have the ability to chelate ametal. Other typical polydentate ligands include for example,ethylenediamine, acetylacetonoate, ethylenediaminetetraacetate (EDTA)hydroxyethyl ethylenediaminetetriacetate (HEDTA), glycine, andpolyphosphates such a pyrophosphate or triphosphate.

The amount of chelating agent 156 included in the resistance-reducingconductive layer 150 may vary depending upon the composition of thesuspension material 54, the composition of the chelating agent 156, thecomposition of the first and second leads 112, 114, or other factors.For most applications, however, it is believed that the chelating agent156 will comprise between approximately 0.1% to 20% by weight of theresistance-reducing conductive layer 150, although other quantities ofchelating agent may be used. In one embodiment, the resistance of theelectrical connection 100 having first and second conductive leads 112,114 electrically coupled using the resistance-reducing conductive layer150 composed of 90% Ablebond® 8360 (by weight) and 10% oxalic acid (byweight) was reduced by about 30% compared with a control connectionformed using only Ablebond® 8360.

FIGS. 5A and 5B are schematic representations of first and secondmechanisms 202, 204, respectively, of a resistance-reducing reaction 200in accordance with one embodiment of the invention. FIG. 5Aschematically shows the first mechanism 202 involving a removal ofaluminum oxide 206 from the surfaces of the first and second aluminumleads 112, 114 by forming a soluble aluminum-ligand complex 208. Whilenot being bound by theory, the chelating agent 156 (in this case oxalicacid) is believed to react with the aluminum oxide 206 to produce thesoluble aluminum-ligand complex 208 (in this case aluminum-oxalate) andwater 210. FIG. 5B schematically shows the second mechanism 204involving the passivation of oxide-free aluminum 214 by forming hydrogenbonds 212 between the chelating agent and the aluminum. Thus, becausethe aluminum oxides 206 are removed from the surfaces of the first andsecond aluminum leads 112, 114, and the oxide-free aluminum surfaces 214are passivated, the electrical resistance of the electrical connection100 is reduced.

Although the first and second leads 112, 114 have been described asbeing aluminum leads, the resistance-reducing conductive layer 150 maybe used with leads formed from a variety of metals, including, forexample, divalent or trivalent metals such as aluminum copper, gold,nickel, platinum or silver. Also, the leads may be formed from a varietyof alloys of conductive materials, including, for example, AlCu(typically 0.5 to 2% of Cu), AlSi (typically 1% Si), or AlSiCu, or otheralloys of aluminum, copper, gold, nickel, platinum or silver.

Furthermore, although the resistance-reducing reaction 200 isrepresented in FIGS. 5A and 5B as having first and second mechanisms202, 204 involving oxalic acid as the chelating agent, it should beunderstood that a variety of chelating agents may be included in theresistance-reducing conductive layer 150, and that various chelatingagents may involve a greater number of mechanisms than therepresentative mechanisms shown in FIGS. 5A and 5B and described above.Similarly, the resistance-reducing reaction 200 is not limited to theparticular aluminum oxide 206 shown in FIGS. 5A and 5B, but may involvethe removal of any number of oxidized forms of the metal, including forexample, metal ions.

The resistance-reducing conductive layer 150 advantageously reduces theelectrical resistance of the electrical connection 100 compared with theprior art method. Because the modified suspension medium 154 contains achelating agent 156, the aluminum oxides 206 which exist on the firstand second leads 112, 114 are removed by forming a soluble aluminumcomplex 208, and the resulting oxide-free aluminum is passivated byforming hydrogen bonds 212. The resistance of the electrical connection100 is lowered, resulting in improved signal strength, decreased powerconsumption, and decreased waste heat generation.

The resistance-reducing conductive layer 150 is not limited to thecombination of a chelating agent with Ablebond® 8360. The layer 150 maybe formed by combining a variety of chelating agents with a variety ofisotropically or anisotropically conductive materials, including thosehaving polymeric adhesive suspension materials, as long as thecomponents of the suspension materials, or the solvents or curing agentsused to cure the suspension materials, do not alter the chelating agentor inhibit the mechanisms of the resistance-reducing reaction.Conductive adhesives formulated with hydrophilic components (e.g.epoxies) or a hydrophilic solvent/diluent (e.g. butyrolactone) maydesirably increase the solubility of the chelating agent, improving thedistribution of the chelating agent within the layer 150, and thus, theuniformity of the resistance-reducing reaction between the layer and theleads.

FIG. 6 is a partial cross-sectional view of an electronic assembly 240having a resistance-reducing anisotropically conductive layer 250 inaccordance with an alternate embodiment of the invention. As shown inFIG. 6, the electronic assembly 240 includes a die 10 having a pair ofbond pads 12 electrically coupled to a corresponding pair of contactpads 22 of a circuit board 20 by a resistance-reducing anisotropicallyconductive layer 250. The resistance-reducing anisotropically conductivelayer 250 includes a plurality of conductive particles 252 suspended ina modified suspension material 254, formed as described above from acombination of a chelating agent 156 and a known anisotropicallyconductive adhesive (e.g. Ablebond® 8360). In one embodiment, thechelating agent 156 is blended approximately uniformly within a portionof the conductive adhesive locally disposed between the conductiveleads. In another embodiment, the chelating agent 156 is uniformlyblended substantially with whole portion of the conductive adhesive.

The electronic assembly 240 shown in FIG. 6 advantageously improves theelectrical conductivity (reduces the electrical resistivity) of theconnections between the bond pads 12 and the corresponding contact pads22 compared with the prior art method of attachment shown in FIG. 2 anddescribed above. Because the electrical resistance is reduced, thestrength of the signals transmitted between the bond pads 12 and thecontact pads 22 is improved, the power consumption and the waste heatgenerated by the electronic assembly 240 is reduced.

FIG. 7 is a partial cross-sectional view of a stacked die assembly 300having a plurality of resistance-reducing isotropically conductivelayers in accordance with another embodiment of the invention. In thisembodiment, the stacked die assembly 300 includes an inner die 310having a plurality of first bond pads 12 electrically coupled to aplurality of corresponding contact pads 22 on a circuit board 20. Eachfirst bond pad 12 is coupled to a contact pad 22 by a firstresistance-reducing conductive layer 350 including a plurality of firstconductive particles 352 suspended in a first suspension material 354.As described above with respect to the leads 112, 114 shown in FIG. 4,the first bond pads 12 and the contact pads 22, are formed of conductivematerials, such as aluminum, copper, gold, nickel, platinum, silver oralloys containing such conductive materials.

The inner die 310 also includes a plurality of second bond pads 313facing away from the circuit board 20. An outer die 330 having aplurality of third bond pads 312 is positioned on top of the inner die310, each of the third bond pads 312 being attached to one of the secondbond pads 313 of the inner die 10 by a second resistance-reducingconductive layer 360. Again, the second bond pads 313 and the third bondpads 312 are formed of conductive materials, such as aluminum, copper,silver, or gold, or alloys containing such conductive materials. Theouter die 330 may send and receive signals from the circuit board 20through the internal circuitry (not shown) of the inner die 310.

As shown in FIG. 7, the advantages of the resistance-reducing conductivelayers 350, 360 may be realized in combination with the space-savingadvantages of the stacked die assembly 300. The composition (orproperties) of the first resistance-reducing conductive layers 350 maybe the same as, or different from, the composition (or properties) ofthe second resistance-reducing conductive layers 360. For example, thefirst layers 350 may be isotropically conductive, and the second layers360 may be anisotropically conductive. Or the first layers 350 may havea higher reflow temperature than the second layers 360 to improvefabrication or reworking of the stacked die assembly 300. Overall, theelectrical resistance of the connections between the first bond pads 12and the contact pads 22, and the second bond pads 313 and the third bondpads 314, are lowered, resulting in improved signal strengths, decreasedpower consumption, and decreased waste heat generation.

FIG. 8 is a partial cross-sectional view of an electrical connection 400in accordance with another embodiment of the invention. In theembodiment, the electrical connection 400 includes a first conductivelead 412 formed on a substrate 420, and a second conductive lead 414also formed on the substrate 420. A resistance-reducing conductive layer450 is formed on a portion of the substrate 420 and on a portion of eachof the leads 412, 414. In this embodiment, the resistance-reducingconductive layer 450 may be an isotropically conductive layer, or an“x-axis” anisotropically conductive layer.

In the electrical connection 400, the advantages of resistance-reducingconductive layers are achieved in an embodiment in which the layer andthe conductive leads are formed on the same substrate 420. Thus, thereis no need to squeeze or pinch the layer 450 between the leads 412, 414in order to form the desired resistance-reduced electrical connection.The resistance-reducing reaction between the chelating agent and theconductive materials of the conductive leads removes conductive materialoxides from the leads 412, 414 and may also passivate the oxide-freelead surfaces, thereby lowering the resistance of the electricalconnection 400.

The detailed descriptions of the above embodiments are not exhaustivedescriptions of all embodiments contemplated by the inventors to bewithin the scope of the invention. Indeed, persons skilled in the artwill recognize that certain elements of the above-described embodimentsmay variously be combined or eliminated to create further embodiments,and such further embodiments fall within the scope and teachings of theinvention. It will also be apparent to those of ordinary skill in theart that the above-described embodiments may be combined in whole or inpart to create additional embodiments within the scope and teachings ofthe invention.

Thus, although specific embodiments of, and examples for, the inventionare described herein for illustrative purposes, various equivalentmodifications are possible within the scope of the invention, as thoseskilled in the relevant art will recognize. The teachings providedherein can be applied to other resistance-reducing conductive adhesives,and to other apparatus and methods of attaching electronic componentsusing resistance-reducing conductive adhesives, and not just to theembodiments described above and shown in the accompanying figures.Accordingly, the scope of the invention should be determined from thefollowing claims.

What is claimed is:
 1. A resistance-reducing conductive adhesive,comprising: a first quantity of a conductive adhesive; and a secondquantity of a chelating agent selected from the group consisting ofoxalic acid, malonic acid, succinate citric acid, polyphosphate,ethylenediamine, acetylacetonoate, glycine, EDTA and HEDTA combined withthe first quantity of the conductive adhesive, wherein the conductiveadhesive comprises a hydrophilic adhesive, wherein the second quantityfurther comprises a value within the range from approximately 0.1percent by weight to approximately 20 percent by weight, inclusive. 2.The resistance-reducing conductive adhesive of claim 1 wherein theconductive adhesive comprises an anisotropically conductive adhesive. 3.The resistance-reducing conductive adhesive of claim 1 wherein theconductive adhesive comprises a conductive epoxy.
 4. Theresistance-reducing conductive adhesive of claim 1 wherein the chelatingagent comprises a polydentate ligand.
 5. The resistance-reducingconductive adhesive of claim 4 wherein the polydentate ligand isselected from the group consisting of a polyphosphate, ethylenediamine,acetylacetonoate, glycine, EDTA, and HEDTA.
 6. The resistance-reducingconductive adhesive of claim 4 wherein the polydentate ligand isselected from the group consisting of oxalate, malonate, succinate andcitrate.
 7. The resistance-reducing conductive adhesive of claim 1wherein the chelating agent comprises oxalic acid.
 8. Theresistance-reducing conductive adhesive of claim 1 wherein the chelatingagent comprises citric acid.
 9. The resistance-reducing conductiveadhesive of claim 1 wherein the chelating agent comprises malonic acid.10. The resistance-reducing conductive adhesive of claim 1 wherein thechelating agent comprises succinic acid.
 11. A resistance-reducingconductive adhesive for electrically coupling a first conductive leadwith a second conductive lead, comprising: a conductive adhesive havinga plurality of conductive particles disposed within a suspensionmaterial; and a chelating agent selected from the group consisting ofoxalic acid, malonic acid, succinate citric acid, polyphosphate,ethylenediamine, acetylacetonoate, glycine, EDTA and HEDTA approximatelyuniformly blended with a portion of the conductive adhesive, thechelating agent being chemically reactive with a metal to form a solublemetal-ligand complex, wherein the chelating agent further comprises aquantity of the chelating agent in the range of approximately 0.1percent by weight to approximately 20 percent by weight, inclusive. 12.The resistance-reducing conductive adhesive of claim 11 wherein thechelating agent is selected from the group consisting of oxalate,malonate, succinate and citrate.
 13. The resistance-reducing conductiveadhesive of claim 11 wherein the metal is a divalent or trivalent metal.14. The resistance-reducing conductive adhesive of claim 11 wherein themetal is selected from the group consisting of aluminum, copper, gold,nickel, platinum and silver.
 15. The resistance-reducing conductiveadhesive of claim 11 wherein the metal is aluminum.
 16. Theresistance-reducing conductive adhesive of claim 11 wherein thechelating agent is reactive with an oxide form of the metal.
 17. Theresistance-reducing conductive adhesive of claim 11 wherein thechelating agent forms hydrogen bonds with an oxide-free form of themetal.
 18. The resistance-reducing conductive adhesive of claim 11wherein the conductive adhesive comprises an isotropically conductiveadhesive.
 19. The resistance-reducing conductive adhesive of claim 11wherein the conductive adhesive comprises a hydrophilic material. 20.The resistance-reducing conductive adhesive of claim 11 wherein theportion of the conductive adhesive uniformly blended with the chelatingagent is locally disposed between the first and second conductive leads.21. A resistance-reducing conductive adhesive, comprising: a firstquantity of a conductive adhesive; and a second quantity of a chelatingagent selected from the group consisting of oxalic acid, malonic acid,succinate citric acid, polyphosphate, ethylenediamine, acetylacetonoate,glycine, EDTA and HEDTA combined with the first quantity of theconductive adhesive, wherein the second quantity comprises a valuewithin the range from approximately 0.1 percent by weight toapproximately 20 percent by weight, inclusive.
 22. Theresistance-reducing conductive adhesive of claim 21 wherein theconductive adhesive comprises an anisotropically conductive adhesive.23. The resistance-reducing conductive adhesive of claim 21 wherein theconductive adhesive comprises a conductive epoxy.
 24. Theresistance-reducing conductive adhesive of claim 21 wherein theconductive adhesive comprises a hydrophilic adhesive.
 25. Theresistance-reducing conductive adhesive of claim 21 wherein thepolydentate ligand is selected from the group consisting of apolyphosphate, ethylenediamine, acetylacetonoate, glycine, EDTA, andHEDTA.
 26. The resistance-reducing conductive adhesive of claim 21wherein the chelating agent comprises a polydentate ligand.
 27. Theresistance-reducing conductive adhesive of claim 26 wherein thepolydentate ligand is selected from the group consisting of oxalate,malonate, succinate and citrate.
 28. A resistance-reducing conductiveadhesive, comprising: a first quantity of a conductive adhesive; and asecond quantity of a chelating agent selected from the group consistingof oxalic acid, malonic acid, succinate citric acid, polyphosphate,ethylenediamine, acetylacetonoate, glycine, EDTA and HEDTA combined withthe first quantity of the conductive adhesive, wherein the conductiveadhesive comprises a hydrophilic adhesive, wherein the second quantitycomprises 10 percent by weight.
 29. The resistance-reducing conductiveadhesive of claim 28 wherein the conductive adhesive comprises ananisotropically conductive adhesive.
 30. The resistance-reducingconductive adhesive of claim 28 wherein the conductive adhesivecomprises a conductive epoxy.
 31. The resistance-reducing conductiveadhesive of claim 28 wherein the chelating agent comprises a polydentateligand.
 32. The resistance-reducing conductive adhesive of claim 31wherein the polydentate ligand is selected from the group consisting ofa polyphosphate, ethylenediamine, acetylacetonoate, glycine, EDTA, andHEDTA.
 33. The resistance-reducing conductive adhesive of claim 31wherein the polydentate ligand is selected from the group consisting ofoxalate, malonate, succinate and citrate.
 34. The resistance-reducingconductive adhesive of claim 28 wherein the chelating agent comprisesoxalic acid.
 35. The resistance-reducing conductive adhesive of claim 28wherein the chelating agent comprises citric acid.
 36. Theresistance-reducing conductive adhesive of claim 28 wherein thechelating agent comprises malonic acid.
 37. The resistance-reducingconductive adhesive of claim 28 wherein the chelating agent comprisessuccinic acid.
 38. A resistance-reducing conductive adhesive,comprising: a first quantity of a conductive adhesive; and a secondquantity of a chelating agent selected from the group consisting ofoxalic acid, malonic acid, succinate citric acid, polyphosphate,ethylenediamine, acetylacetonoate, glycine, EDTA and HEDTA combined withthe first quantity of the conductive adhesive, wherein the conductiveadhesive comprises a hydrophilic adhesive, wherein the first quantityfurther comprises 90 percent by weight.
 39. The resistance-reducingconductive adhesive of claim 38 wherein the conductive adhesivecomprises an anisotropically conductive adhesive.
 40. Theresistance-reducing conductive adhesive of claim 38 wherein theconductive adhesive comprises a conductive epoxy.
 41. Theresistance-reducing conductive adhesive of claim 38 wherein thechelating agent comprises a polydentate ligand.
 42. Theresistance-reducing conductive adhesive of claim 41 wherein thepolydentate ligand is selected from the group consisting of apolyphosphate, ethylenediamine, acetylacetonoate, glycine, EDTA, andHEDTA.
 43. The resistance-reducing conductive adhesive of claim 41wherein the polydentate ligand is selected from the group consisting ofoxalate, malonate, succinate and citrate.
 44. The resistance-reducingconductive adhesive of claim 38 wherein the chelating agent comprisesoxalic acid.
 45. The resistance-reducing conductive adhesive of claim 38wherein the chelating agent comprises citric acid.
 46. Theresistance-reducing conductive adhesive of claim 38 wherein thechelating agent comprises malonic acid.
 47. The resistance-reducingconductive adhesive of claim 38 wherein the chelating agent comprisessuccinic acid.